This invention relates to a magnetic/electric field measuring device by means of an electron beam, which is capable of measuring quantitatively magnetic or electric field generated on a surface of a sample and measuring the distribution thereof in real time.
Several methods are known, by which magnetic stray field is detected by means of an electron beam. In a prior art example, which is nearest to this invention among them, deflection of an electron beam is sensed by a detector for detecting the incident position of the electron beam and magnetic stray field is calculated on the basis thereof (IEEE Trans. Magnetics, MAG 20 No. 5 (1986) p. 866-p. 868). By this method the electron beam is made to pass pallarelly to a surface of a magnetic recording head or a magnetic tape and the position of the arrival of the electron beam deflected by magnetic stray field is sensed, on the basis of which the intensity and the direction of the magnetic stray field are calculated. A microchannel plate (hereinbelow abbreviated to MCP), a phosphor screen and a television camera are used for the detection of the impingement position of the electron beam. The bright position generated by the incident electron beam is sensed by the television camera, the image of which is taken in a digital video frame memory and treated further in a CPU so that the distribution of the magnetic stray field is obtained.
By this method there are three restrictions stated below.
Firstly a video memory is necessary, which stores the position of the bright point on the trajectory of the bright point resulting from displacement of the electron beam in the form of an image. Therefore the device processing data stored in the memory and calculating the intensity of the magnetic field is large. In addition it is impossible to detect and display in real time the positional distribution of the magnetic stray field in synchronism with the scanning with the electron beam.
Secondly the positional resolving power of the electron beam incident position is limited by the channel diameter of the MCP, which is several .mu.m.
Thirdly, when the electron beam is focused on a measurement point in the proximity of the surface of the sample, it becomes broader on the MCP. As a result, the bright point on the phosphor screen has a large diameter. Consequently it is impossible to detect extremely small positional variations.